Question

During breathing, the lung alveoli expands and relaxes quickly. Which kind of tissue enables the flexibility in doing so?

• A. Squamous epithelium
• B.
  Columnar epithelium
• C. Cuboidal epithelium
• D. Pseudostratified epithelium

Answer 1

The correct option is A Squamous epithelium


Squamous epithelium forms the lining of coelomic cavities and occurs in the alveoli of lungs, lining of the blood and lymph vessels, etc. Alveoli of lungs or air sacs consists of plate-like or scale-like polygonal cells of squamous epithelium surrounded by collagen and elastin fibres that provide flexibility to alveoli. It enables them to expand and recoil easily during breathing. Squamous epithelium also allows easy exchange of materials across them through diffusion.


Cuboidal epithelium are comprised of thick cells that participate in secretion, excretion and absorption. They form the lining of salivary duct, nephrons etc.

Columnar epithelium lines the inner layer of small intestine.

Epithelial tissues which are arranged in various layers are called stratified epithelium. Pseudostratified epithelium does not contain various layers but they appear to have several layers due to non- uniform arrangement of nucleus.